Fuck AAs , not enough power. They can however use any number of user replaceable, user chargeable LiIon batteries.

I don't want to have to pay a subscription for physical disposable fuel pods for my controller, and it would be really nice if plugging it in cut down on input delay.

Batteries and lack of audio are my only gripes with the steam controller. I still think it's better than every other controller, but I wish it had those. At least though, valve said it will be easy to disassemble with a screwdriver, so we will have a way to replace the battery with an after market one when it dies.

I'm not aware of any controller that can charge NiMH batteries tho. I think the hardware for that would weight as much as the entire controller. Also NiMH batteries don't do well with continuous charging via dock, unlike lithium batteries.